The overall objectives of this trial are to evaluate the biodistribution, tumor targeting properties and pharmacokinetics of a radiolabeled anti-CEA (Carcinoembryonic Antigen) antibody for therapy; To begin to evaluate its anti-tumor effects and to determine the highest, safest dose (maximum tolerated dose) that can be administered with stem cell and G-CSF (Granulocyte Colony Stimulating Factor) support. Physician Eligibility Summary: Histologic diagnosis of breast cancer; CEA (Carcinoembryonic Antigen) producing breast tumor; Evidence of metastatic disease (Stage IV); Must meet or exceed a Karnofsky Performance Status of 70% (Patient cares for self, but is unable to carry on normal activity or to do active work); Age greater than or equal to 18 years; Prior radiation therapy, immunotherapy, or chemotherapy completed 4 weeks prior to study entry; Patients who received whole pelvis radiation therapy or radiation therapy to greater than 40% of bone marrow are ineligible; Patients with brain involvement or greater than 20% bone marrow involvement are ineligible.